Quadrature combined doherty amplifiers

ABSTRACT

Apparatus and methods for quadrature combined Doherty amplifiers are provided herein. In certain embodiments, a separator is used to separate a radio frequency (RF) input signal into a plurality of input signal components that are amplified by a pair of Doherty amplifiers operating in quadrature. Additionally, a combiner is used to combine a plurality of output signal components generated by the pair of Doherty amplifiers, thereby generating an RF output signal exhibiting quadrature balancing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/724,943, filed Dec. 23, 2019 and titled “QUADRATURE COMBINED DOHERTYAMPLIFIERS,” which is a continuation of U.S. application Ser. No.16/190,923, filed Nov. 14, 2018 and titled “QUADRATURE COMBINED DOHERTYAMPLIFIERS,” which claims the benefit of priority under 35 U.S.C. § 119of U.S. Provisional Patent Application No. 62/590,941, filed Nov. 27,2017 and titled “QUADRATURE COMBINED DOHERTY AMPLIFIERS,” which isherein incorporated by reference in its entirety.

BACKGROUND Field

Embodiments of the invention relate to electronic systems, and inparticular, to radio frequency (RF) electronics.

Description of the Related Technology

Power amplifiers can be used to boost or amplify a radio frequency (RF)signal. Thereafter, the boosted RF signal can be used for a variety ofpurposes, including, for example, driving an antenna of an RFcommunication system.

Power amplifiers can be included in a wide variety of communicationdevices, including, but not limited to, mobile phones, tablets, basestations, network access points, laptops, computers, and televisions.Power amplifiers provide amplification to RF signals, which can have afrequency in the range of about 30 kHz to 300 GHz, such as in the rangeof about 500 MHz to about 6 GHz for certain communications standards.

SUMMARY

In certain embodiments, the present disclosure relates to a radiofrequency system. The radio frequency system includes a separatorconfigured to separate a radio frequency input signal into a first pairof input signal components and a second pair of input signal componentshaving a quadrature phase relationship with respect to the first pair ofinput signal components. The radio frequency system further includes afirst Doherty amplifier configured to generate a first pair of amplifiedsignal components based on amplifying the first pair of input signalcomponents, a second Doherty amplifier configured to generate a secondpair of amplified signal components based on amplifying the second pairof input signal components, and a combiner configured to generate aradio frequency output signal based on combining the first pair ofamplified signal components and the second pair of amplified signalcomponents.

In various embodiments, the first Doherty amplifier includes a firstpair of cascode amplification stages, and the second Doherty amplifierincludes a second pair of cascode amplification stages.

In a number of embodiments, the first pair of input signal componentshave a phase difference of about ninety degrees, and the second pair ofinput signal components have a phase difference of about ninety degrees.

In several embodiments, the combiner includes a first power combinerconfigured to generate a first combined signal based on combining thefirst pair of amplified signal components, a second power combinerconfigured to generate a second combined signal based on combining thesecond pair of amplified signal components, and a third power combinerconfigured to generate the radio frequency output signal based oncombining the first combined signal and the second combined signal.

In various embodiments, the combiner includes a first plurality ofpassive elements configured to generate a first combined signal based oncombining the first pair of amplified signal components, a secondplurality of passive elements configured to generate a second combinedsignal based on combining the second pair of amplified signalcomponents, and a power combiner configured to generate the radiofrequency output signal based on combining the first combined signal andthe second combined signal. According to a number of embodiments, thefirst plurality of passive elements includes an inductor connectedbetween a peaking output and a carrier output of the first Dohertyamplifier, a first capacitor connected between the peaking output andground, and a second capacitor connected between the carrier output andground.

In some embodiments, the combiner includes a first pair of quarterwavelength transmission line sections operable to generate a firstcombined signal based on combining the first pair of amplified signalcomponents, a second pair of quarter wavelength transmission linesections operable to generate a second combined signal based oncombining the second pair of amplified signal components, and a powercombiner configured to generate the radio frequency output signal basedon combining the first combined signal and the second combined signal.

In several embodiments, the separator includes a first power splitterconfigured to separate the radio frequency input signal into a firstseparated signal component and a second separated signal component, asecond power splitter configured to separate the first separated signalcomponent into the first pair of input signal components, and a thirdpower splitter configured to separate the second separated signalcomponent into the second pair of input signal components.

In a number of embodiments, the separator includes a power splitter anda balun configured to operate in combination with one another togenerate the first pair of input signal components and the second pairof input signal components.

In various embodiments, the combiner includes a power combiner includingan input port, a thru port, a first conductive coil connecting the inputport to the thru port, an isolation port adjacent to the input port, acoupling port adjacent to the thru port, a second conductive coilconnecting the isolation port to the coupling port, a first center tapport connected to about a center of the first conductive coil, and asecond center tap port connected to about a center of the secondconductive coil.

In several embodiments, the separator includes a power splitterincluding an input port, a thru port, a first conductive coil connectingthe input port to the thru port, an isolation port adjacent to the inputport, a coupling port adjacent to the thru port, a second conductivecoil connecting the isolation port to the coupling port, a first centertap port connected to about a center of the first conductive coil, and asecond center tap port connected to about a center of the secondconductive coil.

In certain embodiments, the present disclosure relates to a method ofradio frequency signal amplification. The method includes separating aradio frequency input signal into a first pair of input signalcomponents and a second pair of input signal components using aseparator, the second pair of input signal components having aquadrature phase relationship with respect to the first pair of inputsignal components. The method further includes amplifying the first pairof input signal components to generate a first pair of amplified signalcomponents using a first Doherty amplifier, amplifying the second pairof input signal components to generate a second pair of amplified signalcomponents using a second Doherty amplifier, and combining the firstpair of amplified signal components and the second pair of amplifiedsignal components to generate a radio frequency output signal using acombiner.

In various embodiments, amplifying the first pair of input signalcomponents includes amplifying a first input signal component using acascode peaking amplification stage of the first Doherty amplifier andamplifying a second signal component using a cascode carrieramplification stage of the first Doherty amplifier.

In certain embodiments, the present disclosure relates to a mobiledevice. The mobile device includes a transceiver configured to generatea radio frequency input signal, and a front end system including a poweramplifier configured to amplify the radio frequency input signal togenerate a radio frequency output signal. The power amplifier includes aseparator configured to separate the radio frequency input signal into afirst pair of input signal components and a second pair of input signalcomponents having a quadrature phase relationship with respect to thefirst pair of input signal components, a first Doherty amplifierconfigured to generate a first pair of amplified signal components basedon amplifying the first pair of input signal components, a secondDoherty amplifier configured to generate a second pair of amplifiedsignal components based on amplifying the second pair of input signalcomponents, and a combiner configured to generate the radio frequencyoutput signal based on combining the first pair of amplified signalcomponents and the second pair of amplified signal components.

In a number of embodiments, the first Doherty amplifier includes a firstpair of cascode amplification stages, and the second Doherty amplifierincludes a second pair of cascode amplification stages.

In various embodiments, the first pair of input signal components have aphase difference of about ninety degrees, and the second pair of inputsignal components have a phase difference of about ninety degrees.

In several embodiments, the combiner includes a first power combinerconfigured to generate a first combined signal based on combining thefirst pair of amplified signal components, a second power combinerconfigured to generate a second combined signal based on combining thesecond pair of amplified signal components, and a third power combinerconfigured to generate the radio frequency output signal based oncombining the first combined signal and the second combined signal.

In some embodiments, the separator includes a first power splitterconfigured to separate the radio frequency input signal into a firstseparated signal component and a second separated signal component, asecond power splitter configured to separate the first separated signalcomponent into the first pair of input signal components, and a thirdpower splitter configured to separate the second separated signalcomponent into the second pair of input signal components.

In various embodiments, the combiner includes a power combiner includingan input port, a thru port, a first conductive coil connecting the inputport to the thru port, an isolation port adjacent to the input port, acoupling port adjacent to the thru port, a second conductive coilconnecting the isolation port to the coupling port, a first center tapport connected to about a center of the first conductive coil, and asecond center tap port connected to about a center of the secondconductive coil.

In a number of embodiments, the separator includes a power splitterincluding an input port, a thru port, a first conductive coil connectingthe input port to the thru port, an isolation port adjacent to the inputport, a coupling port adjacent to the thru port, a second conductivecoil connecting the isolation port to the coupling port, a first centertap port connected to about a center of the first conductive coil, and asecond center tap port connected to about a center of the secondconductive coil.

In certain embodiments, the present disclosure relates to radiofrequency system. The radio frequency system includes a separatorconfigured to separate a radio frequency input signal into a first pairof input signal components and a second pair of input signal components,a first Doherty amplifier configured to generate a first pair ofamplified signal components based on amplifying the first pair of inputsignal components, a second Doherty amplifier configured to generate asecond pair of amplified signal components based on amplifying thesecond pair of input signal components, and a combiner configured togenerate a radio frequency output signal based on combining the firstpair of amplified signal components and the second pair of amplifiedsignal components. The second Doherty amplifier configured to operate inquadrature with respect to the first Doherty amplifier.

In various embodiments, the first Doherty amplifier includes a firstpair of cascode amplification stages, and the second Doherty amplifierincludes a second pair of cascode amplification stages.

In several embodiments, the first Doherty amplifier includes a firstcarrier amplification stage and a first peaking amplification stage, andthe second Doherty amplifier includes a second carrier amplificationstage and a second peaking amplification stage.

In a number of embodiments, the first pair of input signal componentshave a phase difference of about ninety degrees, and the second pair ofinput signal components have a phase difference of about ninety degrees.

In various embodiments, the combiner includes a first power combinerconfigured to generate a first combined signal based on combining thefirst pair of amplified signal components, a second power combinerconfigured to generate a second combined signal based on combining thesecond pair of amplified signal components, and a third power combinerconfigured to generate the radio frequency output signal based oncombining the first combined signal and the second combined signal.

In some embodiments, the combiner includes a first plurality of passiveelements configured to generate a first combined signal based oncombining the first pair of amplified signal components, a secondplurality of passive elements configured to generate a second combinedsignal based on combining the second pair of amplified signalcomponents, and a power combiner configured to generate the radiofrequency output signal based on combining the first combined signal andthe second combined signal. According to a number of embodiments, thefirst plurality of passive elements includes an inductor connectedbetween a peaking output and a carrier output of the first Dohertyamplifier, a first capacitor connected between the peaking output andground, and a second capacitor connected between the carrier output andground.

In several embodiments, the combiner includes a first pair of quarterwavelength transmission line sections operable to generate a firstcombined signal based on combining the first pair of amplified signalcomponents, a second pair of quarter wavelength transmission linesections operable to generate a second combined signal based oncombining the second pair of amplified signal components, and a powercombiner configured to generate the radio frequency output signal basedon combining the first combined signal and the second combined signal.

In various embodiments, the separator includes a first power splitterconfigured to separate the radio frequency input signal into a firstseparated signal component and a second separated signal component, asecond power splitter configured to separate the first separated signalcomponent into the first pair of input signal components, and a thirdpower splitter configured to separate the second separated signalcomponent into the second pair of input signal components.

In a number of embodiments, the separator includes a power splitter anda balun configured to operate in combination with one another togenerate the first pair of input signal components and the second pairof input signal components.

In some embodiments, the combiner includes a power combiner including aninput port, a thru port, a first conductive coil connecting the inputport to the thru port, an isolation port adjacent to the input port, acoupling port adjacent to the thru port, a second conductive coilconnecting the isolation port to the coupling port, a first center tapport connected to about a center of the first conductive coil, and asecond center tap port connected to about a center of the secondconductive coil. According to several embodiments, the power combinerfurther includes a first capacitor connected between the input port andthe isolation port, and a second capacitor connected between the thruport and the coupling port. In accordance with various embodiments, thepower combiner further includes a third capacitor connected between thefirst center tap port and a reference voltage, and a fourth capacitorconnected between the second center tap and the reference voltage.According to a number of embodiments, the first conductive coil and thesecond conductive coil are each substantially shaped as a figure eight.In according with several embodiments, the first conductive coil and thesecond conductive coil are interleaved.

In a number of embodiments, the separator includes a power splitterincluding an input port, a thru port, a first conductive coil connectingthe input port to the thru port, an isolation port adjacent to the inputport, a coupling port adjacent to the thru port, a second conductivecoil connecting the isolation port to the coupling port, a first centertap port connected to about a center of the first conductive coil, and asecond center tap port connected to about a center of the secondconductive coil. According to several embodiments, the power splitterfurther includes a first capacitor connected between the input port andthe isolation port, and a second capacitor connected between the thruport and the coupling port. In accordance with various embodiments, thepower splitter further includes a third capacitor connected between thefirst center tap port and a reference voltage, and a fourth capacitorconnected between the second center tap and the reference voltage.According to some embodiments, the first conductive coil and the secondconductive coil are each substantially shaped as a figure eight. Inaccordance with several embodiments, the first conductive coil and thesecond conductive coil are interleaved.

In certain embodiments, the present disclosure relates to a poweramplifier. The power amplifier includes a separator configured toseparate a radio frequency input signal into a first signal component, asecond signal component, a third signal component, and a fourth signalcomponent. The power amplifier further includes a first amplifierincluding a first peaking amplification stage configured to generate afirst amplified signal component based on amplifying the first signalcomponent, and a first carrier amplification stage configured togenerate a second amplified signal component based on amplifying thesecond signal component. The power amplifier further includes a secondamplifier including a second peaking amplification stage configured togenerate a third amplified signal component based on amplifying thethird signal component, and a second carrier amplification stageconfigured to generate a fourth amplified signal component based onamplifying the fourth signal component. The power amplifier furtherincludes a combiner configured to generate a radio frequency outputsignal based on combining the first amplified signal component, thesecond amplified signal component, the third amplified signal component,and the fourth amplified signal component.

In a number of embodiments, the first peaking amplification stage is acascode amplification stage.

In several embodiments, the second peaking amplification stage is acascode amplification stage.

In some embodiments, the first carrier amplification stage is a cascodeamplification stage.

In various embodiments, the second carrier amplification stage is acascode amplification stage.

In a number of embodiments, the first signal component and the secondsignal component have substantially a quadrature phase relationship.

In various embodiments, the third signal component and the fourth signalcomponent have substantially a quadrature phase relationship.

In several embodiments, the first signal component and the third signalcomponent have substantially a quadrature phase relationship.

In some embodiments, the second signal component and the fourth signalcomponent have substantially a quadrature phase relationship.

In a number of embodiments, the second signal component and the thirdsignal component have about the same phase.

In various embodiments, the combiner includes a first power combinerconfigured to generate a first combined signal based on combining thefirst amplified signal component and the second amplified signalcomponent, a second power combiner configured to generate a secondcombined signal based on combining the third amplified signal componentand the fourth amplified signal component, and a third power combinerconfigured to generate the radio frequency output signal based oncombining the first combined signal and the second combined signal.

In several embodiments, the combiner includes a first plurality ofpassive elements configured to generate a first combined signal based oncombining the first amplified signal component and the second amplifiedsignal component, a second plurality of passive elements configured togenerate a second combined signal based on combining the third amplifiedsignal component and the fourth amplified signal component, and a powercombiner configured to generate the radio frequency output signal basedon combining the first combined signal and the second combined signal.According to various embodiments, the first plurality of passiveelements includes an inductor connected between an output of the firstpeaking amplification stage and an output of first carrier amplificationstage, a first capacitor connected between the output of the firstpeaking amplification stage and ground, and a second capacitor connectedbetween the output of the first carrier amplification stage and ground.

In a number of embodiments, the combiner includes a first pair ofquarter wavelength transmission line sections operable to generate afirst combined signal based on combining the first amplified signalcomponent and the second amplified signal component, a second pair ofquarter wavelength transmission line sections operable to generate asecond combined signal based on combining the third signal component andthe fourth signal component, and a power combiner configured to generatethe radio frequency output signal based on combining the first combinedsignal and the second combined signal.

In various embodiments, the separator includes a first power splitterconfigured to separate the radio frequency input signal into a firstseparated signal component and a second separated signal component, asecond power splitter configured to separate the first separated signalcomponent into the first signal component and the second signalcomponent, and a third power splitter configured to separate the secondseparated signal component into the third signal component and thefourth signal component.

In several embodiments, the separator includes a power splitter and abalun configured to operate in combination with one another to separatethe radio frequency input signal.

In some embodiments, the combiner includes a power combiner including aninput port, a thru port, a first conductive coil connecting the inputport to the thru port, an isolation port adjacent to the input port, acoupling port adjacent to the thru port, a second conductive coilconnecting the isolation port to the coupling port, a first center tapport connected to about a center of the first conductive coil, and asecond center tap port connected to about a center of the secondconductive coil. According to several embodiments, the power combinerfurther includes a first capacitor connected between the input port andthe isolation port, and a second capacitor connected between the thruport and the coupling port. In accordance with various embodiments, thepower combiner further includes a third capacitor connected between thefirst center tap port and a reference voltage, and a fourth capacitorconnected between the second center tap and the reference voltage.According to a number of embodiments, the first conductive coil and thesecond conductive coil are each substantially shaped as a figure eight.In according with several embodiments, the first conductive coil and thesecond conductive coil are interleaved.

In a number of embodiments, the separator includes a power splitterincluding an input port, a thru port, a first conductive coil connectingthe input port to the thru port, an isolation port adjacent to the inputport, a coupling port adjacent to the thru port, a second conductivecoil connecting the isolation port to the coupling port, a first centertap port connected to about a center of the first conductive coil, and asecond center tap port connected to about a center of the secondconductive coil. According to several embodiments, the power splitterfurther includes a first capacitor connected between the input port andthe isolation port, and a second capacitor connected between the thruport and the coupling port. In accordance with various embodiments, thepower splitter further includes a third capacitor connected between thefirst center tap port and a reference voltage, and a fourth capacitorconnected between the second center tap and the reference voltage.According to some embodiments, the first conductive coil and the secondconductive coil are each substantially shaped as a figure eight. Inaccordance with several embodiments, the first conductive coil and thesecond conductive coil are interleaved.

In certain embodiments, the present disclosure relates to a mobiledevice. The mobile device includes a transceiver configured to generatea radio frequency input signal, an antenna configured to wirelesslytransmit a radio frequency output signal, and a power amplifierincluding a separator configured to separate the radio frequency inputsignal into a first pair of input signal components and a second pair ofinput signal components. The power amplifier further includes a firstDoherty amplifier configured to generate a first pair of amplifiedsignal components based on amplifying the first pair of input signalcomponents, a second Doherty amplifier configured to generate a secondpair of amplified signal components based on amplifying the second pairof input signal components, and a combiner configured to generate theradio frequency output signal based on combining the first pair ofamplified signal components and the second pair of amplified signalcomponents. The second Doherty amplifier is configured to operate inquadrature with respect to the first Doherty amplifier.

In various embodiments, the first Doherty amplifier includes a firstpair of cascode amplification stages, and the second Doherty amplifierincludes a second pair of cascode amplification stages.

In several embodiments, the first Doherty amplifier includes a firstcarrier amplification stage and a first peaking amplification stage, andthe second Doherty amplifier includes a second carrier amplificationstage and a second peaking amplification stage.

In a number of embodiments, the first pair of input signal componentshave a phase difference of about ninety degrees, and the second pair ofinput signal components have a phase difference of about ninety degrees.

In various embodiments, the combiner includes a first power combinerconfigured to generate a first combined signal based on combining thefirst pair of amplified signal components, a second power combinerconfigured to generate a second combined signal based on combining thesecond pair of amplified signal components, and a third power combinerconfigured to generate the radio frequency output signal based oncombining the first combined signal and the second combined signal.

In some embodiments, the combiner includes a first plurality of passiveelements configured to generate a first combined signal based oncombining the first pair of amplified signal components, a secondplurality of passive elements configured to generate a second combinedsignal based on combining the second pair of amplified signalcomponents, and a power combiner configured to generate the radiofrequency output signal based on combining the first combined signal andthe second combined signal. According to a number of embodiments, thefirst plurality of passive elements includes an inductor connectedbetween a peaking output and a carrier output of the first Dohertyamplifier, a first capacitor connected between the peaking output andground, and a second capacitor connected between the carrier output andground.

In several embodiments, the combiner includes a first pair of quarterwavelength transmission line sections operable to generate a firstcombined signal based on combining the first pair of amplified signalcomponents, a second pair of quarter wavelength transmission linesections operable to generate a second combined signal based oncombining the second pair of amplified signal components, and a powercombiner configured to generate the radio frequency output signal basedon combining the first combined signal and the second combined signal.

In various embodiments, the separator includes a first power splitterconfigured to separate the radio frequency input signal into a firstseparated signal component and a second separated signal component, asecond power splitter configured to separate the first separated signalcomponent into the first pair of input signal components, and a thirdpower splitter configured to separate the second separated signalcomponent into the second pair of input signal components.

In a number of embodiments, the separator includes a power splitter anda balun configured to operate in combination with one another togenerate the first pair of input signal components and the second pairof input signal components.

In some embodiments, the combiner includes a power combiner including aninput port, a thru port, a first conductive coil connecting the inputport to the thru port, an isolation port adjacent to the input port, acoupling port adjacent to the thru port, a second conductive coilconnecting the isolation port to the coupling port, a first center tapport connected to about a center of the first conductive coil, and asecond center tap port connected to about a center of the secondconductive coil. According to several embodiments, the power combinerfurther includes a first capacitor connected between the input port andthe isolation port, and a second capacitor connected between the thruport and the coupling port. In accordance with various embodiments, thepower combiner further includes a third capacitor connected between thefirst center tap port and a reference voltage, and a fourth capacitorconnected between the second center tap and the reference voltage.According to a number of embodiments, the first conductive coil and thesecond conductive coil are each substantially shaped as a figure eight.In according with several embodiments, the first conductive coil and thesecond conductive coil are interleaved.

In a number of embodiments, the separator includes a power splitterincluding an input port, a thru port, a first conductive coil connectingthe input port to the thru port, an isolation port adjacent to the inputport, a coupling port adjacent to the thru port, a second conductivecoil connecting the isolation port to the coupling port, a first centertap port connected to about a center of the first conductive coil, and asecond center tap port connected to about a center of the secondconductive coil. According to several embodiments, the power splitterfurther includes a first capacitor connected between the input port andthe isolation port, and a second capacitor connected between the thruport and the coupling port. In accordance with various embodiments, thepower splitter further includes a third capacitor connected between thefirst center tap port and a reference voltage, and a fourth capacitorconnected between the second center tap and the reference voltage.According to some embodiments, the first conductive coil and the secondconductive coil are each substantially shaped as a figure eight. Inaccordance with several embodiments, the first conductive coil and thesecond conductive coil are interleaved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one example of a communication network.

FIG. 2A is a schematic diagram of one embodiment of a quadraturecombined Doherty amplifier.

FIG. 2B is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier.

FIG. 2C is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier.

FIG. 2D is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier.

FIG. 3 is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier.

FIG. 4 is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier.

FIG. 5 is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier.

FIG. 6 is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier.

FIG. 7 is a schematic diagram of one example of a 3 dB hybrid couplerfor serving as a power combiner or splitter.

FIG. 8 is a schematic diagram of another example of a 3 dB hybridcoupler for serving as a power combiner or splitter.

FIG. 9 is a schematic diagram of a power combiner/splitter with coilwinding according to one embodiment.

FIG. 10 is a schematic diagram of one embodiment of a powercombining/splitting system.

FIG. 11 is a schematic diagram of a power combiner/splitter with coilwinding according to another embodiment.

FIG. 12 is a schematic diagram of another embodiment of a powercombiner/splitter with connected capacitors for broadband operation.

FIG. 13 is a schematic diagram of a power combiner/splitter with coilwinding according to another embodiment.

FIG. 14A illustrates a plot of amplitude imbalance versus frequency forone example of a combiner/splitter.

FIG. 14B illustrates a plot of phase imbalance versus frequency for oneexample of a combiner/splitter.

FIG. 14C illustrates a plot of S-parameters in decibels versus frequencyfor one example of a combiner/splitter.

FIG. 14D illustrates a plot of S-parameters in degrees versus frequencyfor one example of a combiner/splitter.

FIG. 15A illustrates a plot of amplitude imbalance versus frequency foranother example of a combiner/splitter.

FIG. 15B illustrates a plot of phase imbalance versus frequency foranother example of a combiner/splitter.

FIG. 15C illustrates a plot of S-parameters in decibels versus frequencyfor another example of a combiner/splitter.

FIG. 15D illustrates a plot of S-parameters in degrees versus frequencyfor another example of a combiner/splitter.

FIG. 15E illustrates a plot of S-parameters in decibels versus frequencyfor another example of a combiner/splitter.

FIG. 15F illustrates a plot of S-parameters in degrees versus frequencyfor another example of a combiner/splitter.

FIG. 16 illustrates one example of simulation results of S21 versusfrequency for various example amplifiers.

FIG. 17 illustrates one example of simulation results of adjacentchannel leakage ratio (ACLR) versus frequency for a Doherty amplifierand for a quadrature combined Doherty amplifier.

FIG. 18 illustrates one example of simulation results of saturatedoutput power (Psat) versus frequency for a Doherty amplifier and for aquadrature combined Doherty amplifier.

FIG. 19 illustrates one example of simulation results of power-addedefficiency (PAE) versus frequency for a Doherty amplifier and for aquadrature combined Doherty amplifier.

FIG. 20 illustrates one example of simulation results of gain versusfrequency for a Doherty amplifier and for a quadrature combined Dohertyamplifier.

FIG. 21A illustrates a Smith chart of load impedance versus voltagestanding wave ratio (VSWR) for one example of a quadrature combinedDoherty amplifier in a low power mode.

FIG. 21B illustrates a Smith chart of impedance seen by the carrieramplifiers versus VSWR for one example of a quadrature combined Dohertyamplifier in a low power mode.

FIG. 21C illustrates a Smith chart of impedance seen by the peakingamplifiers versus VSWR for one example of a quadrature combined Dohertyamplifier in a low power mode.

FIG. 21D illustrates a Smith chart of load impedance versus VSWR for oneexample of a quadrature combined Doherty amplifier in a high power mode.

FIG. 21E illustrates a Smith chart of impedance seen by the carrieramplifiers versus VSWR for one example of a quadrature combined Dohertyamplifier in a high power mode.

FIG. 21F illustrates a Smith chart of impedance seen by the peakingamplifiers versus VSWR for one example of a quadrature combined Dohertyamplifier in a high power mode.

FIG. 22A illustrates a Smith chart of load impedance VSWR for anotherexample of a quadrature combined Doherty amplifier in a low power mode.

FIG. 22B illustrates a Smith chart of impedance seen by the carrieramplifiers versus VSWR for another example of a quadrature combinedDoherty amplifier in a low power mode.

FIG. 22C illustrates a Smith chart of impedance seen by the peakingamplifiers versus VSWR for another example of a quadrature combinedDoherty amplifier in a low power mode.

FIG. 22D illustrates a Smith chart of load impedance versus VSWR foranother example of a quadrature combined Doherty amplifier in a highpower mode.

FIG. 22E illustrates a Smith chart of impedance seen by the carrieramplifiers versus VSWR for another example of a quadrature combinedDoherty amplifier in a high power mode.

FIG. 22F illustrates a Smith chart of impedance seen by the peakingamplifiers versus VSWR for another example of a quadrature combinedDoherty amplifier in a high power mode.

FIG. 23 is a schematic diagram of one embodiment of a mobile device.

FIG. 24 is a schematic diagram of a power amplifier system according toone embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

The International Telecommunication Union (ITU) is a specialized agencyof the United Nations (UN) responsible for global issues concerninginformation and communication technologies, including the shared globaluse of radio spectrum.

The 3rd Generation Partnership Project (3GPP) is a collaboration betweengroups of telecommunications standard bodies across the world, such asthe Association of Radio Industries and Businesses (ARIB), theTelecommunications Technology Committee (TTC), the China CommunicationsStandards Association (CCSA), the Alliance for TelecommunicationsIndustry Solutions (ATIS), the Telecommunications Technology Association(TTA), the European Telecommunications Standards Institute (ETSI), andthe Telecommunications Standards Development Society, India (TSDSI).

Working within the scope of the ITU, 3GPP develops and maintainstechnical specifications for a variety of mobile communicationtechnologies, including, for example, second generation (2G) technology(for instance, Global System for Mobile Communications (GSM) andEnhanced Data Rates for GSM Evolution (EDGE)), third generation (3G)technology (for instance, Universal Mobile Telecommunications System(UMTS) and High Speed Packet Access (HSPA)), and fourth generation (4G)technology (for instance, Long Term Evolution (LTE) and LTE-Advanced).

The technical specifications controlled by 3GPP can be expanded andrevised by specification releases, which can span multiple years andspecify a breadth of new features and evolutions.

In one example, 3GPP introduced carrier aggregation (CA) for LTE inRelease 10. Although initially introduced with two downlink carriers,3GPP expanded carrier aggregation in Release 14 to include up to fivedownlink carriers and up to three uplink carriers. Other examples of newfeatures and evolutions provided by 3GPP releases include, but are notlimited to, License Assisted Access (LAA), enhanced LAA (eLAA),Narrowband Internet-of-Things (NB-IOT), Vehicle-to-Everything (V2X), andHigh Power User Equipment (HPUE).

3GPP introduced Phase 1 of fifth generation (5G) technology in Release15, and plans to introduce Phase 2 of 5G technology in Release 16(targeted for 2019). Subsequent 3GPP releases will further evolve andexpand 5G technology. 5G technology is also referred to herein as 5G NewRadio (NR).

5G NR supports or plans to support a variety of features, such ascommunications over millimeter wave spectrum, beam forming capability,high spectral efficiency waveforms, low latency communications, multipleradio numerology, and/or non-orthogonal multiple access (NOMA). Althoughsuch RF functionalities offer flexibility to networks and enhance userdata rates, supporting such features can pose a number of technicalchallenges.

The teachings herein are applicable to a wide variety of communicationsystems, including, but not limited to, communication systems usingadvanced cellular technologies, such as LTE-Advanced, LTE-Advanced Pro,and/or 5G NR.

FIG. 1 is a schematic diagram of one example of a communication network10. The communication network 10 includes a macro cell base station 1, asmall cell base station 3, and various examples of user equipment (UE),including a first mobile device 2 a, a wireless-connected car 2 b, alaptop 2 c, a stationary wireless device 2 d, a wireless-connected train2 e, and a second mobile device 2 f.

Although specific examples of base stations and user equipment areillustrated in FIG. 1, a communication network can include base stationsand user equipment of a wide variety of types and/or numbers.

For instance, in the example shown, the communication network 10includes the macro cell base station 1 and the small cell base station3. The small cell base station 3 can operate with relatively lowerpower, shorter range, and/or with fewer concurrent users relative to themacro cell base station 1. The small cell base station 3 can also bereferred to as a femtocell, a picocell, or a microcell. Although thecommunication network 10 is illustrated as including two base stations,the communication network 10 can be implemented to include more or fewerbase stations and/or base stations of other types.

Although various examples of user equipment are shown, the teachingsherein are applicable to a wide variety of user equipment, including,but not limited to, mobile phones, tablets, laptops, IoT devices,wearable electronics, customer premises equipment (CPE),wireless-connected vehicles, wireless relays, and/or a wide variety ofother communication devices.

The illustrated communication network 10 of FIG. 1 supportscommunications using a variety of technologies, including, for example,4G LTE, 5G NR, and wireless local area network (WLAN), such as Wi-Fi.Although various examples of communication technologies have beenprovided, the communication network 10 can be adapted to support a widevariety of communication technologies.

Various communication links of the communication network 10 have beendepicted in FIG. 1. The communication links can be duplexed in a widevariety of ways, including, for example, using frequency-divisionduplexing (FDD) and/or time-division duplexing (TDD). FDD is a type ofradio frequency communications that uses different frequencies fortransmitting and receiving signals. FDD can provide a number ofadvantages, such as high data rates and low latency. In contrast, TDD isa type of radio frequency communications that uses about the samefrequency for transmitting and receiving signals, and in which transmitand receive communications are switched in time. TDD can provide anumber of advantages, such as efficient use of spectrum and variableallocation of throughput between transmit and receive directions.

In certain implementations, user equipment can communication with a basestation using one or more of 4G LTE, 5G NR, and Wi-Fi technologies. Incertain implementations, enhanced license assisted access (eLAA) is usedto aggregate one or more licensed frequency carriers (for instance,licensed 4G LTE and/or 5G NR frequencies), with one or more unlicensedcarriers (for instance, unlicensed Wi-Fi frequencies).

The communication links can operate over a wide variety of frequencies.In certain implementations, communications are supported using 5G NRtechnology over one or more frequency bands that are less than 6Gigahertz (GHz) and/or over one or more frequency bands that are greaterthan 6 GHz. In one embodiment, one or more of the mobile devices supporta HPUE power class specification.

In certain implementations, a base station and/or user equipmentcommunicates using beamforming. For example, beamforming can be used tofocus signal strength to overcome path losses, such as high lossassociated with communicating over high signal frequencies. In certainembodiments, user equipment, such as one or more mobile phones,communicate using beamforming on millimeter wave frequency bands in therange of 30 GHz to 300 GHz and/or upper centimeter wave frequencies inthe range of 6 GHz to 30 GHz, or more particularly, 24 GHz to 30 GHz.

Different users of the communication network 10 can share availablenetwork resources, such as available frequency spectrum, in a widevariety of ways.

In one example, frequency division multiple access (FDMA) is used todivide a frequency band into multiple frequency carriers. Additionally,one or more carriers are allocated to a particular user. Examples ofFDMA include, but are not limited to, single carrier FDMA (SC-FDMA) andorthogonal FDMA (OFDMA). OFDM is a multicarrier technology thatsubdivides the available bandwidth into multiple mutually orthogonalnarrowband subcarriers, which can be separately assigned to differentusers.

Other examples of shared access include, but are not limited to, timedivision multiple access (TDMA) in which a user is allocated particulartime slots for using a frequency resource, code division multiple access(CDMA) in which a frequency resource is shared amongst different usersby assigning each user a unique code, space-divisional multiple access(SDMA) in which beamforming is used to provide shared access by spatialdivision, and non-orthogonal multiple access (NOMA) in which the powerdomain is used for multiple access. For example, NOMA can be used toserve multiple users at the same frequency, time, and/or code, but withdifferent power levels.

Enhanced mobile broadband (eMBB) refers to technology for growing systemcapacity of LTE networks. For example, eMBB can refer to communicationswith a peak data rate of at least 10 Gbps and a minimum of 100 Mbps foreach user. Ultra-reliable low latency communications (uRLLC) refers totechnology for communication with very low latency, for instance, lessthan 2 milliseconds. uRLLC can be used for mission-criticalcommunications such as for autonomous driving and/or remote surgeryapplications. Massive machine-type communications (mMTC) refers to lowcost and low data rate communications associated with wirelessconnections to everyday objects, such as those associated with Internetof Things (IoT) applications.

The communication network 10 of FIG. 1 can be used to support a widevariety of advanced communication features, including, but not limitedto, eMBB, uRLLC, and/or mMTC.

Examples of Quadrature Combined Doherty Amplifiers

A Doherty amplifier includes a carrier amplification stage and a peakingamplification stage for providing amplification to a radio frequency(RF) input signal. Additionally, the Doherty amplifier combines acarrier signal component from the carrier amplification stage and apeaking signal component from the peaking stage to generate an amplifiedoutput signal.

The linearity of a Doherty amplifier is based on a balance of amplitudeand phase of the carrier signal component relative to the peaking signalcomponent. When a Doherty amplifier drives a mismatched load, thelinearity of the Doherty amplifier is degraded. For example, an AM-AMlinearity characteristic of a Doherty amplifier with mismatched load canexhibit a step or kink having a direction that depends on a phase ofmismatch. A load mismatch of a Doherty amplifier can arise from avariety of sources, including, but not limited to variation in S11versus frequency of a transmit filter, duplexer, antenna, and/or othercomponents that load to the Doherty amplifier.

Furthermore, the sharpness of the Doherty amplifier's gain step responseunder mismatch can increase with the efficiency of the Dohertyamplifier. Thus, a high efficiency Doherty amplifier can suffer fromexcessively high adjacent channel leakage ratio (ACLR) and/orout-of-band emissions when operating with a mismatched load.

Quadrature combined Doherty amplifiers are provided herein. In certainembodiments, a separator is used to separate an RF input signal into aplurality of input signal components that are amplified by a pair ofDoherty amplifiers operating in quadrature. Additionally, a combiner isused to combine a plurality of output signal components generated by thepair of Doherty amplifiers, thereby generating an RF output signalexhibiting quadrature balancing.

By using a quadrature combined Doherty amplifier, flatter gain versusfrequency, lower variation in saturated output power (Psat), and/orsuperior power-added efficiency (PAE) can be achieved. Furthermore,distortion arising from mismatch is reduced since each Doherty amplifierof the pair can be pulled in opposite directions to cause partialcancellation of intermodulation distortion (IMD) products. Moreover, aquadrature combined Doherty amplifier can include a hybrid terminationresistor, which can absorb a reflected wave to thereby reduce outputripple and/or eliminate multiple reflections between the amplifier and amismatched load.

In certain implementations, a Doherty amplifier includes a carrieramplification stage and/or a peaking amplification stage implementedusing a cascode-based amplification stage. Using cascode amplificationstages can realize a number of advantages, including, but not limitedto, higher output impedance, proportionality of gain to load impedance,higher gain due to reduced Miller effect, and/or quasi-unilateralbehavior. In certain implementations, a first input stage drives thecarrier amplification stage and a second input stage drives the peakingamplification stage.

Gain modulation by varying load results in linear operation of thequadrature combined Doherty amplifier as well as reduced mismatch of thepeaking amplification stages in a high power range, for instance, from 6dB back-off to saturated power. Although mismatch of the carrieramplification stages can increase, the carrier amplification stages ofeach Doherty amplifier of the pair are pulled in opposite directions,and thus overall distortion is reduced.

The quadrature combined Doherty amplifiers are applicable to a widevariety of RF communication systems, including, but not limited to,smartphones, laptops, handsets, wearable electronics, and/or tablets. Incertain implementations, the quadrature combined Doherty amplifierserves as a power amplifier (PA) in an RF communication system. Thus,the quadrature combined Doherty amplifier can be used to generate anamplified RF output signal that is wirelessly transmitted via anantenna.

FIG. 2A is a schematic diagram of one embodiment of a quadraturecombined Doherty amplifier 20. The quadrature combined Doherty amplifier20 includes a separator 11, a combiner 12, and a pair of Dohertyamplifiers including a first Doherty amplifier 13 and a second Dohertyamplifier 14.

In the illustrated embodiment, the first Doherty amplifier 13 includes afirst peaking amplification stage 15 and a first carrier amplificationstage 17. Additionally, the second Doherty amplifier 14 includes asecond peaking amplification stage 16 and a second carrier amplificationstage 18. Although the peaking and carrier amplification circuitry ofeach Doherty amplifier is depicted as a single stage, multi-stageimplementations are also possible. For example, an input stage can befurther included for each of the first peaking amplification stage 15,the second peaking amplification stage 16, the first carrieramplification stage 17, and the second carrier amplification stage 18.

As shown in FIG. 2A, the separator 11 separates the RF input signalRF_IN into a plurality of input signal components 21 a-21 d that areamplified by the pair of Doherty amplifiers. Additionally, the pair ofDoherty amplifiers generate a plurality of output signal components 22a-22 d that are combined using the combiner 12 to generate the RF outputsignal RF_OUT. The first Doherty amplifier 13 amplifies a first pair ofthe input signal components 21 a, 21 b and the second Doherty amplifier14 amplifies a second pair of the input signal components 21 c, 21 d.

In certain implementations, the first input signal component 21 a andthe second input signal component 21 b have a quadrature phaserelationship, or a phase separation of about 90°. Additionally, thethird input signal component 21 c and the fourth input signal component21 d have a quadrature phase relationship. Furthermore, in certainconfigurations, the first input signal component 21 a and the thirdinput signal component 21 c have a quadrature phase relationship, andthe second input signal component 21 b and the fourth input signalcomponent 21 d have a quadrature phase relationship. Thus, the inputsignals 21 a, 21 b to the first Doherty amplifier 13 can have aquadrature phase relationship to the input signals 21 c, 21 d to thesecond Doherty amplifier 14.

The quadrature combined Doherty amplifier 20 can exhibit relatively flatgain versus frequency, relatively low variation in Psat, and/orexcellent PAE performance. Furthermore, distortion arising from mismatchof the amplifier's load is reduced since the first Doherty amplifier 13and the second Doherty amplifier 14 can be pulled in opposite directionsto cause partial cancellation of intermodulation distortion (IMD)products. Moreover, the combiner 12 can include a hybrid terminationresistor, which can absorb a reflected wave to thereby reduce outputripple and/or eliminate multiple reflections between the amplifier 20and a mismatched load.

FIG. 2B is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier 40. The quadrature combined Doherty amplifier40 includes a separator 11, a combiner 12, and a pair of Dohertyamplifiers including a first Doherty amplifier 23 and a second Dohertyamplifier 24. The first Doherty amplifier 23 includes a first cascodepeaking amplification stage 25 and a first cascode carrier amplificationstage 27. The second Doherty amplifier 24 includes a second cascodepeaking amplification stage 26 and a second cascode carrieramplification stage 28.

The quadrature combined Doherty amplifier 40 of FIG. 2B is similar tothe quadrature combined Doherty amplifier 20 of FIG. 2A, except that thequadrature combined Doherty amplifier 40 of FIG. 2B includes a specificimplementation of carrier and peaking amplification stages.

In the illustrated embodiment, the Doherty amplifiers are eachimplemented with cascode amplification stages. For example, the firstcascode peaking amplification stage 25 includes a gain transistor 31 a,a cascode transistor 32 a, an input biasing inductor 33 a, and a DC feedinductor 34 a. Additionally, the first cascode carrier amplificationstage 27 includes a gain transistor 31 b, a cascode transistor 32 b, aninput biasing inductor 33 b, and a DC feed inductor 34 b. Furthermore,the second cascode peaking amplification stage 26 includes a gaintransistor 31 c, a cascode transistor 32 c, an input biasing inductor 33c, and a DC feed inductor 34 c. Additionally, the second cascode carrieramplification stage 28 includes a gain transistor 31 d, a cascodetransistor 32 d, an input biasing inductor 33 d, and a DC feed inductor34 d.

As shown in FIG. 2B, the input biasing inductors 33 a-33 d serve to biasthe gates of the gain transistors 31 a-31 d, respectively, with a gatebias voltage VG. Additionally, the cascode transistors 32 a-32 d arebiased with a cascode gate voltage VCAS. Furthermore, the DC feedinductors 34 a-34 d serve to provide the drains of the cascodetransistors 32 a-32 d, respectively, with a power supply voltage VDD.

Although one implementation of cascode-based amplification stages forDoherty amplifiers is shown in FIG. 2B, the teachings herein areapplicable to other implementations of amplification stages for Dohertyamplifiers, including, but not limited to, common source amplificationstages, common emitter amplification stages, and other configurations ofcascode-based amplification stages. For example, the teachings hereinare also applicable to cascode amplification stages using bipolartransistors, or a combination of field-effect transistors and bipolartransistors. Furthermore, the teachings here are applicable to differentimplementations of biasing.

Using cascode amplification stages in the quadrature combined Dohertyamplifier 40 can realize a number of advantages, including, but notlimited to, higher output impedance, proportionality of gain to loadimpedance, higher gain due to reduced Miller effect (presence of thecascode transistors 32 a-32 d reduces drain voltage variation of thegain transistors 31 a-31 d, and thus the gate-to-drain capacitances oftransistors 31 a-31 d have a smaller impact on gain), and/orquasi-unilateral behavior.

Furthermore, gain modulation by varying load results in linear operationof the quadrature combined Doherty amplifier 40 as well as reducedmismatch of the cascode peaking amplification stages in a high powerrange, for instance, from 6 dB back-off to saturated power. Althoughmismatch of the cascode carrier amplification stages can increase, thefirst cascode carrier amplification stage 27 and the second cascodecarrier amplification stage 28 are pulled in opposite directions, andthus overall distortion is reduced.

FIG. 2C is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier 40′. The quadrature combined Dohertyamplifier 40′ includes a separator 11, a combiner 12, and a pair ofDoherty amplifiers including a first Doherty amplifier 23′ and a secondDoherty amplifier 24′. The first Doherty amplifier 23′ includes a firstcascode peaking amplification stage 25′ and a first cascode carrieramplification stage 27′. The second Doherty amplifier 24′ includes asecond cascode peaking amplification stage 26′ and a second cascodecarrier amplification stage 28′.

The Doherty amplifier 40′ of FIG. 2C is similar to the Doherty amplifier40 of FIG. 2B, except that a bipolar transistor implementation is shownrather than a FET implementation. For example, the first cascode peakingamplification stage 25′ includes a gain transistor 31 a′, a cascodetransistor 32 a′, an input biasing inductor 33 a, and a DC feed inductor34 a. Additionally, the first cascode carrier amplification stage 27′includes a gain transistor 31 b′, a cascode transistor 32 b′, an inputbiasing inductor 33 b, and a DC feed inductor 34 b. Furthermore, thesecond cascode peaking amplification stage 26′ includes a gaintransistor 31 c′, a cascode transistor 32 c′, an input biasing inductor33 c, and a DC feed inductor 34 c. Additionally, the second cascodecarrier amplification stage 28′ includes a gain transistor 31 d′, acascode transistor 32 d′, an input biasing inductor 33 d, and a DC feedinductor 34 d.

As shown in FIG. 2C, the input biasing inductors 33 a-33 d serve to biasthe bases of the gain transistors 31 a′-31 d′, respectively, with a basebias voltage VB. Additionally, the bases of the cascode transistors 32a′-32 d′ are biased with a cascode base voltage VCAS. Furthermore, theDC feed inductors 34 a-34 d serve to provide the collectors of thecascode transistors 32 a′-32 d′, respectively, with a power supplyvoltage VCC.

FIG. 2D is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier 69. The quadrature combined Doherty amplifier69 includes a separator 11, a combiner 12, and a pair of Dohertyamplifiers including a first Doherty amplifier 47 and a second Dohertyamplifier 48.

As shown in FIG. 2D, the first Doherty amplifier 47 includes a firstpeaking input stage 55, a first cascode peaking amplification stage 25,a first carrier input stage 57, and a first cascode carrieramplification stage 27. Additionally, the second Doherty amplifier 48includes a second peaking input stage 56, a second cascode peakingamplification stage 26, a second carrier input stage 58, and a secondcascode carrier amplification stage 28.

The quadrature combined Doherty amplifier 69 of FIG. 2D is similar tothe quadrature combined Doherty amplifier 40 of FIG. 2B, except that thequadrature combined Doherty amplifier 69 of FIG. 2D further includes thefirst peaking input stage 55, the second peaking input stage 56, thefirst carrier input stage 57, and the second carrier input stage 58.

In certain embodiments herein, multi-stage peaking amplifiers andmulti-stage carrier amplifiers are used in a quadrature combined Dohertyamplifier. Although one such embodiment is depicted in FIG. 2D, otherimplementations are possible.

In the illustrated embodiment, the first peaking input stage 55 includesa gain transistor 66 a, an input biasing inductor 67 a, and a DC feedinductor 68 a. Additionally, the first carrier input stage 57 includes again transistor 66 b, an input biasing inductor 67 b, and a DC feedinductor 68 b. Furthermore, the second peaking input stage 56 includes again transistor 66 c, an input biasing inductor 67 c, and a DC feedinductor 68 c. Additionally, the second carrier input stage 58 includesa gain transistor 66 d, an input biasing inductor 67 d, and a DC feedinductor 68 d.

As shown in FIG. 2D, the input biasing inductors 67 a-67 d serve to biasthe gates of the gain transistors 66 a-66 d, respectively, with a gatebias voltage VGB. Additionally, the DC feed inductors 68 a-68 d serve toprovide the drains of the gain transistors 66 a-66 d, respectively, withthe power supply voltage VDD.

FIG. 3 is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier 50. The quadrature combined Doherty amplifier50 includes a separator 41, a combiner 42, and a pair of Dohertyamplifiers including a first Doherty amplifier 13 and a second Dohertyamplifier 14.

The quadrature combined Doherty amplifier 50 of FIG. 3 is similar to thequadrature combined Doherty amplifier 20 of FIG. 2A, except that thequadrature combined Doherty amplifier 50 of FIG. 3 includes specificimplementations of a separator and a combiner. The separator 41 of FIG.3 illustrates one implementation of the separator 21 of FIG. 2A.Additionally, the combiner 42 of FIG. 3 illustrates one implementationof the combiner 22 of FIG. 2A.

As shown in FIG. 3, the separator 41 includes a first power divider orsplitter 43 a, a second power splitter 43 b, a third power splitter 43c, a first termination resistor 44 a, a second terminal resistor 44 b,and a third termination resistor 44 c. In certain implementations, eachof the termination resistors 44 a-44 c has a resistance of about 50Ω.

In the illustrated embodiment, each power splitter includes an inputport (N), an isolation port (ISO), a thru port (0), and a coupling port(−90). As persons having ordinary skill in the art with appreciate, apower splitter can be used to process an input signal to generate outputsignal components of about equal power and about a 90° phase difference.

In the illustrated embodiment, the first input signal component 21 a hasabout a −180° phase, the second input signal component 21 b has about a−90° phase, the third input signal component 21 c has about a −90°phase, and the fourth input signal component 21 d has about a 0° phase.However, other implementations are possible.

With continuing reference to FIG. 3, the combiner 50 includes a firstpower combiner 45 a, a second power combiner 45 b, a third powercombiner 45 c, and a hybrid termination resistor 46. The power combiners45 a-45 c have similar ports or terminals as the power splitters 43 a-43c, but operate in a reversed configuration to provide power combiningrather than power splitting. In certain implementations, the hybridtermination resistor 46 has a resistance of about 50Ω.

FIG. 4 is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier 60. The quadrature combined Doherty amplifier60 includes a separator 41, a combiner 52, and a pair of Dohertyamplifiers including a first Doherty amplifier 13 and a second Dohertyamplifier 14.

The quadrature combined Doherty amplifier 60 of FIG. 4 is similar to thequadrature combined Doherty amplifier 50 of FIG. 3, except that thequadrature combined Doherty amplifier 60 of FIG. 4 includes a differentimplementation of a combiner 52.

As shown in FIG. 4, the combiner 52 includes a power combiner 45, ahybrid termination resistor 46, a first quarter wavelength (λ/4)transmission line section 53 a, a second quarter wavelength transmissionline section 53 b, a third quarter wavelength transmission line section53 c, and a fourth quarter wavelength transmission line section 53 d.Each of the quarter wavelength transmission line sections 53 a-53 dprovides a phase delay of about 90°, and thus serves as a transmissionline impedance inverter.

The quarter wavelength transmission line sections 53 a-53 d can beimplemented in a wide variety of ways, including, but not limited tousing lumped pi (π) and/or lumped tee (T) sections.

FIG. 5 is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier 70. The quadrature combined Doherty amplifier70 includes a separator 61, a combiner 42, and a pair of Dohertyamplifiers including a first Doherty amplifier 13 and a second Dohertyamplifier 14.

The quadrature combined Doherty amplifier 70 of FIG. 5 is similar to thequadrature combined Doherty amplifier 50 of FIG. 3, except that thequadrature combined Doherty amplifier 70 of FIG. 5 includes a differentimplementation of a separator 61.

As shown in FIG. 5, the separator 61 includes a power splitter 42, atermination resistor 44, and a balun 65.

In certain implementations, the individual core amplifier inputs of thefirst Doherty amplifier 13 and the second Doherty amplifier 14 arematched to 2*Zo (for instance, 100Ω), where Zo is the system impedance(for instance, 50Ω) of the combined quadrature Doherty amplifier.

FIG. 6 is a schematic diagram of another embodiment of a quadraturecombined Doherty amplifier 80. The quadrature combined Doherty amplifier80 includes a separator 61, a combiner 72, and a pair of Dohertyamplifiers including a first Doherty amplifier 13 and a second Dohertyamplifier 14.

The quadrature combined Doherty amplifier 80 of FIG. 6 is similar to thequadrature combined Doherty amplifier 70 of FIG. 5, except that thequadrature combined Doherty amplifier 80 of FIG. 6 includes a differentimplementation of a combiner 72.

As shown in FIG. 6, the combiner 72 includes a power combiner 45, ahybrid termination resistor 46, a first combiner capacitor 73 a, asecond combiner capacitor 73 b, a third combiner capacitor 73 c, afourth combiner capacitor 73 d, a first combiner inductor 74 a, a secondcombiner inductor 74 b, a first DC feed inductor 75 a, and a second DCfeed inductor 75 b.

Using passive components to provide power combining can provide arelatively compact layout, thereby aiding in integration of the combiner72. For example, the simplified semi-lumped implementation of FIG. 6 canbe suitable for applications associated with relaxed output power andconducted harmonics specifications.

In certain implementations, both the inputs and outputs of the firstDoherty amplifier 13 and the second Doherty amplifier 14 are matched to2*Zo (for instance, 100Ω), where Zo is the system impedance (forinstance, 50Ω) of the combined quadrature Doherty amplifier.

Examples of Power Combiners/Splitters

A 3 dB hybrid coupler is a four-port device that can be used to split aninput signal into two signal components with about equal power and aquadrature phase relationship or to combine two signal components into acombined signal while maintaining high port-to-port isolation.

A 3 dB hybrid coupler can serve as a component in a wide variety oftypes of RF circuits, including, but not limited to, Doherty amplifiers.For example, one or more instantiations of 3 dB hybrid couplers can beused as power combiners and/or power splitters in an RF system, such asa Doherty amplifier or quadrature combined Doherty amplifier.

FIG. 7 is a schematic diagram of one example of a 3 dB hybrid coupler120 for serving as a power combiner or splitter. The 3 dB hybrid coupler120 includes a first terminal or port 101, a second port 102, a thirdport 103, a fourth port 104, a first conductive coil 111, and a secondconductive coil 112. In FIG. 7, different layers of conductivemetallization have been represented using different patterns or fills.

In certain implementations, the first port 101 corresponds to an inputport (N), the second port 102 corresponds to a thru port (0°), the thirdport 103 corresponds to an isolation port (ISO), and the fourth port 104corresponds to a coupling port (90°).

As shown in FIG. 7, the first conductive coil or spiral 111 serves toconnect the first port 101 to the second port 102. Additionally, thesecond conductive coil 112 serves to connect the third port 103 to thefourth port 104. The first conductive coil 111 and the second conductivecoil 112 are partially overlaid to provide inductive coupling. Thus, thefirst conductive coil 111 and the second conductive coil 112 aremagnetically or inductively coupled to one another.

The 3 dB hybrid coupler 120 illustrates one example implementation of apower combiner/splitter. One or more instantiations of the 3 dB hybridcoupler 120 can serve, for example, to provide power combining and/orpower splitting in a quadrature combined Doherty amplifier.

FIG. 8 is a schematic diagram of another example of a 3 dB hybridcoupler 140 for serving as a power combiner or splitter. The 3 dB hybridcoupler 140 includes a first terminal or port 121, a second port 122, athird port 123, a fourth port 124, a first conductive coil 131, and asecond conductive coil 132. In FIG. 8, different layers of conductivemetallization have been represented using different patterns or fills.

In certain implementations, the first port 121 corresponds to an inputport (N), the second port 122 corresponds to a thru port (0°), the thirdport 123 corresponds to an isolation port (ISO), and the fourth port 124corresponds to a coupling port (90°).

As shown in FIG. 8, the first conductive coil 131 serves to connect thefirst port 121 to the second port 122. Additionally, the secondconductive coil 132 serves to connect the third port 123 to the fourthport 124. The first conductive coil 131 and the second conductive coil132 are partially overlaid to provide inductive coupling. Thus, thefirst conductive coil 131 and the second conductive coil 132 aremagnetically or inductively coupled to one another.

The 3 dB hybrid coupler 140 illustrates another example implementationof a power combiner/splitter. One or more instantiations of the 3 dBhybrid coupler 140 can serve, for example, to provide power combiningand/or power splitting in a quadrature combined Doherty amplifier.

In certain applications, it is desirable for a power combiner/splitterto have a compact layout and to provide wideband operation.

In certain configurations herein, a power combiner/splitter isimplemented with coils formed on two or more metal layers of asemiconductor chip. For example, two coils with an eight (8) shape canbe formed using adjacent conductive layers of the semiconductor chip.The power combiner/splitter further includes contacts to a center ofeach coil to aid in connecting capacitors and/or other impedance toprovide wideband operation.

Thus, capacitors can connect to center taps of each coil to providetuning to the performance characteristics of the powercombiner/splitter.

In certain implementations, a first coil connects a first port (forinstance, an input port) to a second port (for instance, a thru port),and a second coil connects a third port (for instance, an isolationport) to a fourth port (for instance, a coupling port). Furthermore, thepower combiner/splitter is implemented with a fifth port for connectingto the center tap of the first coil, and a sixth port for connecting toa center tap of the second coil.

To provide wideband operation, capacitors can be connected to the portsof the power combiner/splitter. In certain implementations, a firstcapacitor is connected between the first port and the third port, asecond capacitor is connected between the second port and the fourthport, a third capacitor is connected between the fifth port and areference voltage (for instance, ground), and a fourth capacitor isconnected between the sixth port and the reference voltage. Accordingly,the power combiner/splitter can operate with a relative small number ofexternal capacitors, for instance, four. In contrast, certainconventional power combiners/splitters operate with nine or moreexternal capacitors.

In certain implementations, the coils are implemented such that thefirst port and the third port are relatively close in distance to oneanother (for instance, immediately adjacent ports), and such that thesecond port and the fourth port are relatively close in distance to oneanother (for instance, immediately adjacent ports).

By routing the coils in this manner, ports used for combining andseparating signals are positioned in relative close proximity, which canaid in providing signal connectivity to other RF circuitry.Additionally, implementing the coils in this manner facilitatesconnection of the first capacitor between the first port and the thirdport and of the second capacitor between the second port and the fourthport with low parasitics. Thus, facilitation of connectingcross-coupling capacitors is achieved.

The combiners/splitters can be implemented with integrated quadraturehybrid geometry for wideband operation. The routing of coils can beimplemented to position the combining port and the coupling port next toeach other to facilitate the connection of a cross-coupling capacitor.In certain configurations, +/−0.15 dB magnitude imbalance of thegeometry is greater than about 27%.

In certain implementations, the inter-layer offset can be used to adjustcoil mutual coupling co-efficient, thereby achieving wideband operation.Furthermore, coupling level is relatively easy to change forapplications in which an unequal coupling level is needed (for instance,uneven power splitting).

The combiners/splitters herein can be implemented in a wide variety ofways, for instance, using integrated passive devices (IPD) or laminatetechnology. In certain implementations, the ports of a powercombiner/splitter correspond to pads of a semiconductor die.

FIG. 9 is a schematic diagram of a power combiner/splitter 160 with coilwinding according to one embodiment. The power combiner/splitter 160includes a first port 141, a second port 142, a third port 143, a fourthport 144, a fifth port 145, a sixth port 146, a first conductiveeight-shaped coil 151, and a second conductive eight-shaped coil 152. InFIG. 9, different layers of conductive metallization have beenrepresented using different patterns or fills.

In certain implementations, the first port 141 corresponds to an inputport, the second port 142 corresponds to a thru port, the third port 143corresponds to an isolation port, the fourth port 144 corresponds to acoupling port, the fifth port 145 corresponds to a first coil center tapport, and the sixth port 146 corresponds to a second coil center tapport.

The power combiner/splitter 160 can be used in a wide variety ofapplications. For instance, one or more instantiations of the powercombiner/splitter 160 can serve, for example, to provide power combiningand/or power splitting in a quadrature combined Doherty amplifier.

As shown in FIG. 9, the first conductive eight-shaped coil 151 serves toconnect the first port 141 to the second port 142. Additionally, thesecond conductive eight-shaped coil 152 serves to connect the third port143 to the fourth port 144. The first conductive eight-shaped coil 151and the second conductive eight-shaped coil 152 are partially overlaidto provide inductive coupling.

In the illustrated embodiment, the first conductive eight-shaped coil151 and the second conductive eight-shaped coil 152 are implemented witha shape that is substantially an eight (8). Furthermore the coils arerouted such that the first port 141 is immediately adjacent to the thirdport 143 and such that the second port 142 is immediately adjacent tothe fourth port 144. As shown in FIG. 9, in this embodiment the fifthport 145 is also immediately adjacent to the third port 143, and thesixth port 146 is also immediately adjacent to the fourth port 144.

By routing the coils in this manner, ports used for combining andseparating signals are positioned in relative close proximity, which canaid in providing signal connectivity to other RF circuitry.Additionally, implementing the coils in this manner facilitatesconnection of the first capacitor between the first port and the thirdport and of the second capacitor between the second port and the fourthport with low parasitics. Thus, facilitation of connectingcross-coupling capacitors is achieved.

Thus, capacitors can be connected to the ports of the powercombiner/splitter to provide tuning and/or enhanced bandwidth operation.In certain implementations, a first capacitor is connected between thefirst port 141 and the third port 143, a second capacitor is connectedbetween the second port 142 and the fourth port 144, a third capacitoris connected between the fifth port 145 and a reference voltage (forinstance, ground), and a fourth capacitor is connected between the sixthport 146 and the reference voltage. As shown in FIG. 9, the fifth port145 connects to a center tap of the first conductive eight-shaped coil151, and the sixth port 146 connects to a center tap of the secondconductive eight-shaped coil 152.

By connecting the capacitors and/or other suitable impedance elements inthis manner, wide bandwidth of the power combiner/splitter 160 can beachieved. Accordingly, the power combiner/splitter 160 can operate witha relative small number of external capacitors, for instance, four. Incontrast, certain conventional power combiners/splitters operate withnine or more external capacitors.

Moreover, the power combiner/splitter 160 has a compact layout, whichfacilitates integration into an RF system. In certain implementations,the power combiner/splitter 160 is implemented using IPD and/or laminatetechnology (including, but not limited to, a laminated substrate of amulti-chip module). In certain implementations, the ports of the powercombiner/splitter 160 correspond to pads of a semiconductor die.

In one embodiment, the power combiner/splitter 160 is implemented with atotal area of less than 3 mm², for instance, 1.85 mm×1.5 mm.

FIG. 10 is a schematic diagram of one embodiment of a powercombining/splitting system 210. The power combining/splitting system 210includes a power combiner/splitter 201, a first termination resistor 202a, a second termination resistor 202 b, a third termination resistor 202c, a fourth termination resistor 202 d, a first capacitor 203 a, asecond capacitor 203 b, a third capacitor 203 c, and a fourth capacitor203 d.

As shown in FIG. 10, the power combiner/splitter 201 includes a firstport (1), a second port (2), a third port (3), a fourth port (4), afifth port (5), and a sixth port (6). In certain implementations, thefirst port corresponds to an input port, the second port corresponds toa thru port, the third port corresponds to an isolation port, the fourthport corresponds to a coupling port, the fifth port corresponds to afirst coil center tap port, and the sixth port corresponds to a secondcoil center tap port.

The power combiner/splitter 201 can be implemented in a wide variety ofways, including, but not limited to, using any of the embodiments ofFIG. 9 or FIGS. 11-13. In certain implementations, the powercombiner/splitter 201 is implemented using IPD and/or laminatetechnology, and the termination resistors 202 a-202 d and the capacitors203 a-203 d correspond to components (for instance, surface mountdevices) attached to a laminate.

As shown in FIG. 10, the first capacitor 203 a, is connected between thefirst port and the third port of the power combiner/splitter 201, thesecond capacitor 203 b is connected between the second port and thefourth port of the power combiner/splitter 201, the third capacitor 203c is connected between the fifth port of the power combiner/splitter 201and ground, and the fourth capacitor 203 d is connected between thesixth port of the power combiner/splitter 201 and ground.

As shown in FIG. 10, the combiner/splitter can be implemented with fourcapacitors to provide wideband operation. Additionally, fifth to ninthcapacitors 204 a-204 e, respectively, need not be included. Rather, suchcapacitors can be absorbed into a layout of the power combiner/splitter201, thereby reducing a footprint of the system.

FIG. 11 is a schematic diagram of a power combiner/splitter 240 withcoil winding according to another embodiment. The powercombiner/splitter 240 includes a first port 221, a second port 222, athird port 223, a fourth port 224, a fifth port 225, a sixth port 226, afirst conductive coil 231, and a second conductive coil 232. In FIG. 11,different layers of conductive metallization have been represented usingdifferent patterns or fills.

In certain implementations, the first port 221 corresponds to an inputport, the second port 222 corresponds to a thru port, the third port 223corresponds to an isolation port, the fourth port 224 corresponds to acoupling port, the fifth port 225 corresponds to a first coil center tapport, and the sixth port 226 corresponds to a second coil center tapport.

The power combiner/splitter 240 can be used in a wide variety ofapplications. For instance, one or more instantiations of the powercombiner/splitter 240 can serve, for example, to provide power combiningand/or power splitting in a quadrature combined Doherty amplifier.

As shown in FIG. 11, the first conductive coil 231 serves to connect thefirst port 221 to the second port 222. Additionally, the secondconductive coil 232 serves to connect the third port 223 to the fourthport 224. The first conductive coil 231 and the second conductive coil232 are partially overlaid to provide inductive coupling.

In the illustrated embodiment, the coils are routed such that the firstport 221 is immediately adjacent to the third port 223 and such that thesecond port 222 is immediately adjacent to the fourth port 224.

By routing the coils in this manner, ports used for combining andseparating signals are positioned in relative close proximity, which canaid in providing signal connectivity to other RF circuitry.Additionally, implementing the coils in this manner facilitatesconnection of the first capacitor between the first port and the thirdport and of the second capacitor between the second port and the fourthport with low parasitics. Thus, facilitation of connectingcross-coupling capacitors is achieved.

Thus, capacitors can be connected to the ports of the powercombiner/splitter to provide tuning and/or enhanced bandwidth operation.In certain implementations, a first capacitor is connected between thefirst port 221 and the third port 223, a second capacitor is connectedbetween the second port 222 and the fourth port 224, a third capacitoris connected between the fifth port 225 and a reference voltage, and afourth capacitor is connected between the sixth port 226 and thereference voltage. As shown in FIG. 11, the fifth port 225 connects to acenter tap of the first conductive coil 231, and the sixth port 226connects to a center tap of the second conductive coil 232.

By connecting the capacitors and/or other suitable impedance elements inthis manner, enhanced bandwidth of the power combiner/splitter 240 canbe achieved. Accordingly, the power combiner/splitter 240 can operatewith a relative small number of external capacitors, for instance, four.In contrast, certain conventional power combiners/splitters operate withnine or more external capacitors.

Moreover, the power combiner/splitter 240 has a compact layout, whichfacilitates integration into an RF system. In certain implementations,the power combiner/splitter 240 is implemented using IPD and/or laminatetechnology (including, but not limited to, a laminated substrate of amulti-chip module). In certain implementations, the ports of the powercombiner/splitter 240 connect to pads of a semiconductor die.

FIG. 12 is a schematic diagram of another embodiment of a powercombiner/splitter 240 with connected capacitors for broadband operation.

As shown in FIG. 12, a first capacitor C1 is connected between the firstport 221 and the third port 223. Additionally, a second capacitor C2 isconnected between the second port 222 and the fourth port 224.Furthermore, a third capacitor C3 is connected between the fifth port225 and ground, and a fourth capacitor C4 is connected between the sixthport 226 and ground.

In the illustrated embodiment, the first port corresponds to an inputport, the second port corresponds to a thru port, the third portcorresponds to an isolation port, the fourth port corresponds to acoupling port, the fifth port corresponds to a first coil center tapport, and the sixth port corresponds to a second coil center tap port.

FIG. 13 is a schematic diagram of a power combiner/splitter 260 withcoil winding according to another embodiment. The powercombiner/splitter 260 includes a first port 241, a second port 242, athird port 243, a fourth port 244, a fifth port 245, a sixth port 246, afirst conductive eight-shaped coil 251, and a second conductiveeight-shaped coil 252. In FIG. 13, different layers of conductivemetallization have been represented using different patterns or fills.

The power combiner/splitter 260 of FIG. 13 is similar to the powercombiner/splitter 160 of FIG. 9, except that the power combiner/splitter260 includes a different implementation of routing of the firstconductive eight-shaped coil 251 and the second conductive eight-shapedcoil 252.

As shown in FIG. 13, the coils are routed to include cross-overs 255 tothereby provide interleaving of the coils. Implementing the coils withthe cross-overs 255 in this manner provides a number of advantages, suchas reduced process variations and/or lower performance variation overfrequency.

The power combiners/splitters described above can be implemented in awide variety of RF circuitry. Any of the power combiners/splittersdescribed herein can be used a power combiner and/or as a power splitterin any of the quadrature combined Doherty amplifiers described abovewith respect to FIGS. 2A-6. However, the power combiners/splitters canalso be used in other configurations of RF circuitry.

Examples of Simulation Results

FIGS. 14A-14D illustrate one example of simulation results for acombiner/splitter. The simulation results correspond to plots obtainedby simulating one implementation of the combiner/splitter 260 of FIG.13.

FIG. 14A illustrates one example of a plot 301 of amplitude imbalance(in dB) versus frequency.

FIG. 14B illustrates one example of a plot 302 of phase imbalance (indegrees) versus frequency.

FIG. 14C illustrates one example of S-parameters (in dB) versusfrequency. The graph includes a first plot 311 corresponding toS-parameter dB(1,1), a second plot 312 of corresponding to S-parameterdB(1,2), a third plot 313 corresponding to S-parameter dB(1,3), and afourth plot 314 corresponding to S-parameter dB(1,4), where the firstport (1) is the input port, the second port (2) is the thru port, portthree (3) is the isolation port, and port four (4) is the coupling port.

FIG. 14D illustrates one example of S-parameters (in degrees) versusfrequency. The graph includes a first plot 317 corresponding toS-parameter phase(1,2) and a second plot 318 of S-parameter phase(1,3).

FIGS. 15A-15F illustrate another example of simulation results for acombiner/splitter. The simulation results correspond to plots obtainedby simulating one implementation of the combiner/splitter 160 of FIG. 9.FIGS. 15A-15D correspond to simulated results for an implementationusing an integrated passive devices (IPD) die, while FIGS. 15E-15Fcorrespond to correspond to simulated results for an implementationusing a laminate.

FIG. 15A illustrates another example of a plot 321 of amplitudeimbalance (in dB) versus frequency. As shown in FIG. 15A the simulatedgeometry exhibits a +/−0.15 dB magnitude imbalance over a 200 MHz rangeof frequency.

FIG. 15B illustrates another example of a plot 322 of phase imbalance(in degrees) versus frequency.

FIG. 15C illustrates another example of S-parameters (in dB) versusfrequency. The graph includes a first plot 331 corresponding toS-parameter dB(1,1), a second plot 332 of corresponding to S-parameterdB(1,2), a third plot 333 corresponding to S-parameter dB(1,3), and afourth plot 334 corresponding to S-parameter dB(1,4), where the firstport (1) is the input port, the second port (2) is the thru port, portthree (3) is the isolation port, and port four (4) is the coupling port.

FIG. 15D illustrates another example of S-parameters (in degrees) versusfrequency. The graph includes a first plot 337 corresponding toS-parameter phase(1,2) and a second plot 338 of S-parameter phase(1,3).

FIG. 15E illustrates another example of S-parameters (in dB) versusfrequency. The graph includes a first plot 341 corresponding toS-parameter dB(1,1), a second plot 342 of corresponding to S-parameterdB(1,2), a third plot 343 corresponding to S-parameter dB(1,3), and afourth plot 344 corresponding to S-parameter dB(1,4), where the firstport (1) is the input port, the second port (2) is the thru port, portthree (3) is the isolation port, and port four (4) is the coupling port.

FIG. 15F illustrates another example of S-parameters (in degrees) versusfrequency. The graph includes a first plot 347 corresponding toS-parameter phase(1,2) and a second plot 348 of S-parameter phase(1,3).

FIG. 16 illustrates one example of simulation results of S21 versusfrequency for various example amplifiers. The graph includes a firstplot 351 of S21 versus frequency for a single-ended amplifier, a secondplot 352 of S21 versus frequency for a Doherty amplifier, a third plot353 of S21 versus frequency for a quadrature combined Doherty amplifier,and a fourth plot 354 of load S21 (normalized).

As shown in FIG. 16, the quadrature combined Doherty amplifier providesreduced S21 variation versus frequency, and thus advantageously providesa reduction in gain ripple.

FIG. 17 illustrates one example of simulation results of adjacentchannel leakage ratio (ACLR) versus frequency for a Doherty amplifierand for a quadrature combined Doherty amplifier. The simulation resultsare measured with a typical transmit filter.

As shown in FIG. 17, the quadrature combined Doherty amplifier exhibitsless variation in ACLR versus frequency, and thus exhibits lessvariation in emissions levels across changes in frequency.

FIG. 18 illustrates one example of simulation results of saturatedoutput power (Psat) versus frequency for a Doherty amplifier and for aquadrature combined Doherty amplifier.

The simulation results are measured with a typical transmit filter.Additionally, the results are normalized. As shown in FIG. 18, thequadrature combined Doherty amplifier exhibits less variation in Psatversus frequency.

FIG. 19 illustrates one example of simulation results of power-addedefficiency (PAE) versus frequency for a Doherty amplifier and for aquadrature combined Doherty amplifier.

The simulation results are measured with a typical transmit filter.Additionally, the results are normalized. As shown in FIG. 19, thequadrature combined Doherty amplifier exhibits less variation in PAEversus frequency.

FIG. 20 illustrates one example of simulation results of gain versusfrequency for a Doherty amplifier and for a quadrature combined Dohertyamplifier.

The simulation results are measured with a typical transmit filter.Additionally, the results are normalized. As shown in FIG. 20, thequadrature combined Doherty amplifier exhibits less variation in PAEversus frequency.

FIGS. 21A-21F illustrate one example of simulation results for aquadrature combined Doherty amplifier. The simulation results correspondto plots obtained by simulating one implementation of a quadraturecombined Doherty amplifier using common source amplification stages toimplement the peaking and carrier amplifiers.

The simulation results include Smith charts depicting various impedancetrajectories when varying the load VSWR between 1 and 1.5. FIGS. 21A-21Ccorrespond to simulations of the quadrature combined Doherty amplifierin a low power mode below the 6 dB back off point. Additionally, FIGS.21D-21F correspond to simulations of the quadrature combined Dohertyamplifier in a high power mode between the 6 dB back off point and Psat.

FIG. 21A illustrates a Smith chart of load impedance versus VSWR in thelow power mode.

FIG. 21B illustrates a Smith chart of impedance seen by the carrieramplifiers versus VSWR in the low power mode.

FIG. 21C illustrates a Smith chart of impedance seen by the peakingamplifiers versus VSWR in the low power mode.

FIG. 21D illustrates a Smith chart of load impedance versus VSWR in thehigh power mode.

FIG. 21E illustrates a Smith chart of impedance seen by the carrieramplifiers versus VSWR in the high power mode.

FIG. 21F illustrates a Smith chart of impedance seen by the peakingamplifiers versus VSWR in the high power mode.

FIGS. 22A-22F illustrate another example of simulation results for aquadrature combined Doherty amplifier. The simulation results correspondto plots obtained by simulating one implementation of a quadraturecombined Doherty amplifier using cascode amplification stages toimplement the peaking and carrier amplifiers.

Thus, in contrast to the simulation results of FIGS. 21A-21F whichcorrespond to a quadrature combined Doherty amplifier implemented usingcommon source amplification stages, the simulation results of FIGS.22A-22F correspond to a quadrature combined Doherty amplifierimplemented using cascode stages.

FIG. 22A illustrates a Smith chart of load impedance VSWR in the lowpower mode.

FIG. 22B illustrates a Smith chart of impedance seen by the carrieramplifiers versus VSWR in the low power mode.

FIG. 22C illustrates a Smith chart of impedance seen by the peakingamplifiers versus VSWR in the low power mode.

FIG. 22D illustrates a Smith chart of load impedance versus VSWR in thehigh power mode.

FIG. 22E illustrates a Smith chart of impedance seen by the carrieramplifiers versus VSWR in the high power mode.

FIG. 22F illustrates a Smith chart of impedance seen by the peakingamplifiers versus VSWR in the high power mode.

As shown by a comparison of FIGS. 21A-21F to FIGS. 22A-22F, usingcascode stages reduces the load pull seen by the peaking amplifierstages.

For example, when using common source stages, the same level of mismatchis exhibited as the output of the whole quadrature combined Dohertyamplifier. In contrast, when using cascode stages, mismatch seen by thepeaking stages is reduced, for instance, close to VSWR 1:1 regardless ofload mismatch. Although carrier stages see enlarged mismatch whencascode stages are used, the pull is in opposite directions such thatoverall distortion is reduced.

Although various simulation results have been depicted in FIGS. 14A-22F,persons having ordinary skill in the art will appreciate that simulationresults can vary for a wide variety of reasons, including, but notlimited to, design implementation and/or simulation tools, models andparameters. Furthermore, although the simulations are depicted forvarious frequency ranges and bands, the combiners/splitters herein canoperate over a wide range of frequencies and bands. Accordingly, othersimulation results are possible.

Examples of RF Systems Including Combiners/Splitters and/or QuadratureCombined Doherty Amplifiers

FIG. 23 is a schematic diagram of one embodiment of a mobile device 800.The mobile device 800 includes a baseband system 801, a transceiver 802,a front end system 803, antennas 804, a power management system 805, amemory 806, a user interface 807, and a battery 808.

The mobile device 800 illustrates one example of an RF system that caninclude a power combiner/splitter and/or a quadrature combined Dohertyamplifier implemented in accordance with the teachings herein. Forexample, the front end system 803 can include one or more powercombiners, power splitters, and/or Quadrature combined Dohertyamplifiers implemented in accordance with the teachings herein.

The mobile device 800 can be used communicate using a wide variety ofcommunications technologies, including, but not limited to, 2G, 3G, 4G(including LTE, LTE-Advanced, and LTE-Advanced Pro), 5G NR, WLAN (forinstance, Wi-Fi), WPAN (for instance, Bluetooth and ZigBee), WMAN (forinstance, WiMax), and/or GPS technologies.

The transceiver 802 generates RF signals for transmission and processesincoming RF signals received from the antennas 804. It will beunderstood that various functionalities associated with the transmissionand receiving of RF signals can be achieved by one or more componentsthat are collectively represented in FIG. 23 as the transceiver 802. Inone example, separate components (for instance, separate circuits ordies) can be provided for handling certain types of RF signals.

The front end system 803 aids is conditioning signals transmitted toand/or received from the antennas 804. In the illustrated embodiment,the front end system 803 includes power amplifiers (PAs) 811, low noiseamplifiers (LNAs) 812, filters 813, switches 814, and duplexers 815.However, other implementations are possible.

For example, the front end system 803 can provide a number offunctionalities, including, but not limited to, amplifying signals fortransmission, amplifying received signals, filtering signals, switchingbetween different bands, switching between different power modes,switching between transmission and receiving modes, duplexing ofsignals, multiplexing of signals (for instance, diplexing ortriplexing), or some combination thereof.

In certain implementations, the mobile device 800 supports carrieraggregation, thereby providing flexibility to increase peak data rates.Carrier aggregation can be used for both Frequency Division Duplexing(FDD) and Time Division Duplexing (TDD), and may be used to aggregate aplurality of carriers or channels. Carrier aggregation includescontiguous aggregation, in which contiguous carriers within the sameoperating frequency band are aggregated. Carrier aggregation can also benon-contiguous, and can include carriers separated in frequency within acommon band or in different bands.

The antennas 804 can include antennas used for a wide variety of typesof communications. For example, the antennas 804 can include antennasfor transmitting and/or receiving signals associated with a wide varietyof frequencies and communications standards.

In certain implementations, the antennas 804 support MIMO communicationsand/or switched diversity communications. For example, MIMOcommunications use multiple antennas for communicating multiple datastreams over a single radio frequency channel. MIMO communicationsbenefit from higher signal to noise ratio, improved coding, and/orreduced signal interference due to spatial multiplexing differences ofthe radio environment. Switched diversity refers to communications inwhich a particular antenna is selected for operation at a particulartime. For example, a switch can be used to select a particular antennafrom a group of antennas based on a variety of factors, such as anobserved bit error rate and/or a signal strength indicator.

The mobile device 800 can operate with beamforming in certainimplementations. For example, the front end system 803 can include phaseshifters having variable phase controlled by the transceiver 802.Additionally, the phase shifters are controlled to provide beamformation and directivity for transmission and/or reception of signalsusing the antennas 804. For example, in the context of signaltransmission, the phases of the transmit signals provided to theantennas 804 are controlled such that radiated signals from the antennas804 combine using constructive and destructive interference to generatean aggregate transmit signal exhibiting beam-like qualities with moresignal strength propagating in a given direction. In the context ofsignal reception, the phases are controlled such that more signal energyis received when the signal is arriving to the antennas 804 from aparticular direction. In certain implementations, the antennas 804include one or more arrays of antenna elements to enhance beamforming.

The baseband system 801 is coupled to the user interface 807 tofacilitate processing of various user input and output (I/O), such asvoice and data. The baseband system 801 provides the transceiver 802with digital representations of transmit signals, which the transceiver802 processes to generate RF signals for transmission. The basebandsystem 801 also processes digital representations of received signalsprovided by the transceiver 802. As shown in FIG. 23, the basebandsystem 801 is coupled to the memory 806 of facilitate operation of themobile device 800.

The memory 806 can be used for a wide variety of purposes, such asstoring data and/or instructions to facilitate the operation of themobile device 800 and/or to provide storage of user information.

The power management system 805 provides a number of power managementfunctions of the mobile device 800. In certain implementations, thepower management system 805 includes a PA supply control circuit thatcontrols the supply voltages of the power amplifiers 811. For example,the power management system 805 can be configured to change the supplyvoltage(s) provided to one or more of the power amplifiers 811 toimprove efficiency, such as power added efficiency (PAE).

As shown in FIG. 23, the power management system 805 receives a batteryvoltage from the battery 808. The battery 808 can be any suitablebattery for use in the mobile device 800, including, for example, alithium-ion battery.

FIG. 24 is a schematic diagram of a power amplifier system 840 accordingto one embodiment. The illustrated power amplifier system 840 includes abaseband processor 821, a transmitter 822, a power amplifier (PA) 823, adirectional coupler 824, front-end circuitry 825, and an antenna 826.The illustrated transmitter 822 includes an I/Q modulator 837, a mixer838, and an analog-to-digital converter (ADC) 839. In certainimplementations, the transmitter 822 is included in a transceiver suchthat both transmit and receive functionality is provided.

The power amplifier system 840 illustrates one example of an RF systemthat can include a combiner/splitter and/or a quadrature combinedDoherty amplifier implemented in accordance with the teachings herein.For example, the power amplifier system 840 (for instance, the poweramplifier 823) can include one or more power combiners, power splitters,and/or Quadrature combined Doherty amplifiers implemented in accordancewith the teachings herein.

The baseband processor 821 can be used to generate an in-phase (I)signal and a quadrature-phase (Q) signal, which can be used to representa sinusoidal wave or signal of a desired amplitude, frequency, andphase. For example, the I signal can be used to represent an in-phasecomponent of the sinusoidal wave and the Q signal can be used torepresent a quadrature-phase component of the sinusoidal wave, which canbe an equivalent representation of the sinusoidal wave.

In certain implementations, the I and Q signals can be provided to theI/Q modulator 837 in a digital format. The baseband processor 821 can beany suitable processor configured to process a baseband signal. Forinstance, the baseband processor 821 can include a digital signalprocessor, a microprocessor, a programmable core, or any combinationthereof. Moreover, in some implementations, two or more basebandprocessors 821 can be included in the power amplifier system 840.

The I/Q modulator 837 can be configured to receive the I and Q signalsfrom the baseband processor 821 and to process the I and Q signals togenerate an RF signal. For example, the I/Q modulator 837 can includedigital-to-analog converters (DACs) configured to convert the I and Qsignals into an analog format, mixers for upconverting the I and Qsignals to RF, and a signal combiner for combining the upconverted I andQ signals into an RF signal suitable for amplification by the poweramplifier 823. In certain implementations, the I/Q modulator 837 caninclude one or more filters configured to filter frequency content ofsignals processed therein.

The power amplifier 823 can receive the RF signal from the I/Q modulator837, and when enabled can provide an amplified RF signal to the antenna826 via the front-end circuitry 825.

The front-end circuitry 825 can be implemented in a wide variety ofways. In one example, the front-end circuitry 825 includes one or moreswitches, filters, duplexers, multiplexers, and/or other components. Inanother example, the front-end circuitry 825 is omitted in favor of thepower amplifier 823 providing the amplified RF signal directly to theantenna 826.

The directional coupler 824 senses an output signal of the poweramplifier 823. Additionally, the sensed output signal from thedirectional coupler 824 is provided to the mixer 838, which multipliesthe sensed output signal by a reference signal of a controlledfrequency. The mixer 838 operates to generate a downshifted signal bydownshifting the sensed output signal's frequency content. Thedownshifted signal can be provided to the ADC 839, which can convert thedownshifted signal to a digital format suitable for processing by thebaseband processor 821.

Including a feedback path from the output of the power amplifier 823 tothe baseband processor 821 can provide a number of advantages. Forexample, implementing the baseband processor 821 in this manner can aidin providing power control, compensating for transmitter impairments,and/or in performing digital pre-distortion (DPD). Although one exampleof a sensing path for a power amplifier is shown, other implementationsare possible.

CONCLUSION

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Likewise, the word “connected”, as generally used herein, refers to twoor more elements that may be either directly connected, or connected byway of one or more intermediate elements. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, shall refer to this application as a whole and not toany particular portions of this application. Where the context permits,words in the above Detailed Description using the singular or pluralnumber may also include the plural or singular number respectively. Theword “or” in reference to a list of two or more items, that word coversall of the following interpretations of the word: any of the items inthe list, all of the items in the list, and any combination of the itemsin the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “can,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/orstates are included or are to be performed in any particular embodiment.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A radio frequency system comprising: a separatorconfigured to separate a radio frequency input signal into a firstseparated signal component and a second separated signal component, toseparate the first separated signal component into a first pair of inputsignal components, and to separate the second separated signal componentinto a second pair of input signal components having a quadrature phaserelationship with respect to the first pair of input signal components;a first Doherty amplifier configured to generate a first pair ofamplified signal components based on amplifying the first pair of radiofrequency input signal components; a second Doherty amplifier configuredto generate a second pair of amplified signal components based onamplifying the second pair of input signal components; and a combinerconfigured to generate a radio frequency output signal based the firstpair of amplified signal components and the second pair of amplifiedsignal components, the combiner including first and second conductivecoils at least partially overlaid with respect to one another to provideinductive coupling.
 2. The radio frequency system of claim 1 wherein thefirst Doherty amplifier includes a first pair of cascode amplificationstages, and the second Doherty amplifier includes a second pair ofcascode amplification stages.
 3. The radio frequency system of claim 1wherein the first pair of input signal components have a phasedifference of about ninety degrees, and the second pair of input signalcomponents have a phase difference of about ninety degrees.
 4. The radiofrequency system of claim 1 wherein the combiner includes a plurality ofpassive elements.
 5. The radio frequency system of claim 1 wherein theseparator includes a first power splitter configured to separate theradio frequency input signal into the first separated signal componentand the second separated signal component, a second power splitterconfigured to separate the first separated signal component into thefirst pair of input signal components, and a third power splitterconfigured to separate the second separated signal component into thesecond pair of input signal components.
 6. The radio frequency system ofclaim 1 wherein the separator includes a power splitter and a balunconfigured to operate in combination with one another.
 7. A radiofrequency system comprising: a separator configured to separate a radiofrequency input signal into a first separated signal component and asecond separated signal component, to separate the first separatedsignal component into a first pair of input signal components, and toseparate the second separated signal component into a second pair ofinput signal components having a quadrature phase relationship withrespect to the first pair of input signal components; a first Dohertyamplifier configured to generate a first pair of amplified signalcomponents based on amplifying the first pair of radio frequency inputsignal components; a second Doherty amplifier configured to generate asecond pair of amplified signal components based on amplifying thesecond pair of input signal components; and a combiner configured togenerate a radio frequency output signal based the first pair ofamplified signal components and the second pair of amplified signalcomponents, the combiner including first quarter wavelength transmissionline sections operable to generate a first signal based on the firstpair of amplified signal components, second quarter wavelengthtransmission line sections operable to generate a second signal based onthe second pair of amplified signal components, and the combiner isfurther configured to generate a radio frequency output signal based onthe first signal and the second signal.
 8. The radio frequency system ofclaim 7 wherein the separator includes a first power splitter configuredto separate the radio frequency input signal into the first separatedsignal component and the second separated signal component, a secondpower splitter configured to separate the first separated signalcomponent into the first pair of input signal components, and a thirdpower splitter configured to separate the second separated signalcomponent into the second pair of input signal components.
 9. The radiofrequency system of claim 7 wherein the separator includes a powersplitter and a balun configured to operate in combination with oneanother.
 10. A method of radio frequency signal amplification, themethod comprising: using separator to separate a radio frequency inputsignal into first and second separated signal components, separate thefirst separated signal component into a first pair of input signalcomponents, and separate the second separated signal component into asecond pair of input signals components; amplifying the first pair ofinput signal components to generate a first pair of amplified signalcomponents using a first Doherty amplifier; amplifying the second pairof input signal components to generate a second pair of amplified signalcomponents using a second Doherty amplifier; and generating a radiofrequency output signal based on the first pair of amplified signalcomponents and the second pair of amplified signal components, thegenerating including using a combiner that includes first and secondconductive coils at least partially overlaid with respect to oneanother.
 11. The method of claim 10 wherein amplifying the first pair ofinput signal components includes amplifying a first input signalcomponent using a cascode peaking amplification stage of the firstDoherty amplifier and amplifying a second signal component using acascode carrier amplification stage of the first Doherty amplifier. 12.The method of claim 10 wherein the first Doherty amplifier includes afirst pair of cascode amplification stages, and the second Dohertyamplifier includes a second pair of cascode amplification stages. 13.The method of claim 10 wherein the first pair of input signal componentshave a phase difference of about ninety degrees, and the second pair ofinput signal components have a phase difference of about ninety degrees.14. The method of claim 10 wherein the generating is performed using acombiner that includes a plurality of passive elements.
 15. The methodof claim 10 wherein the separating includes using a first power splitterto separate the radio frequency input signal into the first separatedsignal component and the second separated signal component, using asecond power splitter to separate the first separated signal componentinto the first pair of input signal components, and using a third powersplitter to separate the second separated signal component into thesecond pair of input signal components.
 16. The method of claim 10wherein the separating includes using a power splitter and a balunconfigured to operate in combination with one another.
 17. A mobiledevice comprising: a transceiver configured to generate a radiofrequency input signal; and a power amplifier system configured toamplify the radio frequency input signal to generate a radio frequencyoutput signal, the power amplifier system configured to separate theradio frequency input signal into a first separated signal component anda second separated signal component, to separate the first separatedsignal component into a first pair of input signal components, and toseparate the second separated signal component into a second pair ofinput signal components having a quadrature phase relationship withrespect to the first pair of input signal components, the poweramplifier system including a first Doherty amplifier configured togenerate a first pair of amplified signal components based on amplifyingthe first pair of input signal components, and a second Dohertyamplifier configured to generate a second pair of amplified signalcomponents based on amplifying the second pair of input signalcomponents, and the power amplifier system further including a combinerconfigured to generate the radio frequency output signal based on thefirst pair of amplified signal components and the second pair ofamplified signal components, the combiner including first and secondconductive coils at least partially overlaid with respect to one anotherto provide inductive coupling.
 18. The mobile device of claim 17 whereinthe first Doherty amplifier includes a first pair of cascodeamplification stages, and the second Doherty amplifier includes a secondpair of cascode amplification stages.
 19. The mobile device of claim 17wherein the first pair of input signal components have a phasedifference of about ninety degrees, and the second pair of input signalcomponents have a phase difference of about ninety degrees.
 20. A methodof radio frequency signal amplification, the method comprising: usingseparator to separate a radio frequency input signal into first andsecond separated signal components, separate the first separated signalcomponent into a first pair of input signal components, and separate thesecond separated signal component into a second pair of input signalscomponents; amplifying the first pair of input signal components togenerate a first pair of amplified signal components using a firstDoherty amplifier; amplifying the second pair of input signal componentsto generate a second pair of amplified signal components using a secondDoherty amplifier; with first quarter wavelength transmission linesections, generating a first signal based on the first pair of amplifiedsignal components; with second quarter wavelength transmission linesections, generating a second signal based on the second pair ofamplified signal components; and generating a radio frequency outputsignal based on the first signal and the second signal.